The dark kangaroo mouse is strictly nocturnal (1) (3) (5), only venturing out during the cooler desert nights when relative humidity is at its highest (3). This jumping rodent species is most active within the first two hours after sunset (1) (8) (9), when it will forage for food out in open areas away from dense vegetation cover (5) (8).
The diet of the dark kangaroo mouse consists mainly of small seeds (1) (3) (5) (6) (8) (9), which it carries in its external cheek pouches back to its underground burrow system (4) (5), where it stores the food in a cache (1) (4). The dark kangaroo mouse also eats small insects (1) (5) (6) (8) (9), such as beetles and butterfly larvae (9), particularly in the summer months (4). In addition, the dark kangaroo mouse has been reported to occasionally consume green vegetation (3) (9).
The dark kangaroo mouse does not appear to actively drink water (1) (5). Instead, it relies upon the water in its food (5) (6), and reduces water loss by producing concentrated urine and dry faeces (5).
Interestingly, the dark kangaroo mouse also stores food as body fat within the bulge in the centre of its tail (4) (5) (7), which enlarges during the summer as fat is deposited, and then diminishes in size during hibernation as it is used as a source of energy (5) (7). This is a unique feature among small mammals native to North America (5).
During its foraging expeditions, the dark kangaroo mouse is vulnerable to a number of potential predators, including owls, foxes and badgers (1).
The underground burrow systems excavated by the dark kangaroo mouse are relatively simple and unbranched (6), reaching lengths of up to 1.8 metres (3), and rarely being more than 30 centimetres deep (3) (6). The entrance to the burrow is usually located near or under a shrub (3) (5), and it is plugged by the dark kangaroo mouse when it returns after a night of foraging, to prevent water evaporation (3).
Between November and March, the dark kangaroo mouse retires to its burrow to hibernate during the harsh, cold winter (5) (8). After emerging from hibernation in the spring, the breeding season takes place (8). Each litter produced by the female dark kangaroo mouse contains between two and seven young (1) (4) (5) (8), with the majority of litters being born in May and June (1). It is thought that more than one litter is produced per season (1) (5) (8).
The male dark kangaroo mouse aggressively defends its territory, which can be up to 6,600 square metres in size, against others of its kind. Female dark kangaroo mice also establish territories, but these are generally much smaller than those of the male, with an average size of just 400 square metres (4).